1. Field of the Invention
Heretofore, the most common liquid fuel burners for furnaces, incinerators, boilers, gas turbines and jet engines have used air vanes to swirl air for combustion around a region where fuel is injected into the combustion chamber. Such burner systems employ various flow patterns within their combustion chambers, but none have employed large scale recirculation of products of combustion and a subsequent mixing with fuel to produce substantial fuel gasification. Yet without such recirculation and mixing to produce gasification, typical vane swirl burners pyrolyze a portion of the fuel to be burned and form carbon within the flame. Fuel pyrolization results in a luminous prematurely ignited and incompletely mixed flame containing unburned carbon particles.
Vaporization of fuel prior to combustion has been employed in various burners by using a separate fuel vaporizing chamber or additional ducting serving solely to provide recirculation and consequent gasification of fuel. Also, a swirl burner that achieved fuel gasification prior to combustion by recirculation of products of combustion is described in Schindler and Ranz, Recirculation in a Vortex-Stabilized Oil Flame, 1965 API Research Conference on Distillate Fuel Combustion, Conference Paper CP 65-1. Such burner was built by the University of Minnesota and utilized combustion product recirculation to produce gaseous combustion of No. 2 fuel oil. Swirl in the University of Minnesota burner was caused by using a nozzle block that was rotated at high speeds (4000-5000 RPM) and included 212 circular air orifices. A fine mesh screen was disposed above the orifices to eliminate excessive divergence of the air jets emanating therefrom.
The present invention differs from the above described burners in that no rotating parts, vaporizing surfaces or separate vaporizing chambers are located within the burner and no ducting is employed to route recirculating products of combustion. Yet the present invention provides recirculation of a substantial portion of the products of combustion for vaporizing primarily all fuel introduced into the combustion chamber, and also provides thorough fuel, combustion products and air mixing in order that combustion is maintained with less than, equal to or more than stoichiometric quantities of fuel and air, as desired, to achieve a predominantly blue, clean burning flame.